This invention relates polyurethanes and to compositions of relatively high equivalent weight active hydrogen compounds and alkylene glycols, said compositions containing materials that make the compositions useful in preparing polyurethanes.
In making polyurethanes mixtures of a relatively high equivalent weight active hydrogen compound and a relatively low equivalent weight chain extender compound are reacted with a polyisocyanate. Using alkylene glycols as chain extenders often produces advantageous properties in resulting polyurethanes.
In such glycol-extended active hydrogen compound compositions, amine compounds and other compounds having nitrogen to hydrogen bonds (N--H) are also frequently useful. Amines can be present for a variety of functions. For instance, an amine compound can additionally provide catalysis, chain extension, aid in mold release or other function. Amines useful as chain extenders or cross-linking agents, for instance, are described in U.S. Pat. Nos. 4,218,543; 4,269,945; 4,433,067 and 4,444,910. Use of amines as compatibilizing agents, for instance, is described in U.S. application Ser. Number 935,356, filed Nov. 6, 1986. Use as an active hydrogen component, for instance, is described in U.S. Pat. Nos. 4,719,247 and 4,742,091. Use in an internal mold release composition, for instance, is described in U.S. application Ser. No. 570,141, filed Jan. 12, 1984 to Meyer et al. and in U.S. Pat. No. 4,585,803. Other N--H containing compounds are exemplified by urea compounds such as are used in the teachings of U.S. Pat. Nos. 4,485,031 and 4,485,032.
In active hydrogen compositions containing glycols and amine compounds, however, certain common catalysts for forming polyurethanes such as dialkyl tin dicarboxylates, dialkyl tin thioglycolates, and dialkyl tin dimaleates are often observed to lose activity over time and especially on exposure to heat. Precipitates are often observed in such compositions. Loss of activity and precipitate formation can interfere with subsequent polyurethane formation because activity of the compositions varies with storage time and conditions. Similar problems are also noted when compounds such as ureas having N--H groups are present in place of the amines.
It would, therefore, be desirable to prepare active hydrogen compositions having glycols, compounds having groups with N--H structures and catalysts which do not lose substantial activity in the presence of such compositions.